Hopper gas eliminator



y 3, 1932-- F. HOKE ETAL 1,856,557

HOPPER GAS ELIMINATOR Filed Dec. 18, 1930 I N VEN TORS.

A TTORNEYJI .0 conditions,

- Patented May 3, 1932 .UNITED STATES PATENT OFFICE coRronArIoN HOPPER GAS ELIMINATOR Application filed December 18, 1930. Serial No. 503,125.

This invention relates to means for eliminating so-called hopper gas in the operation of Stoker-fired boilers and furnaces.

Where a mechanical stoker is used with a forced draft fan, it is common practice to introduce the fuel and air through different conduits, the air being discharged through tuyeres on either side of the retort through which-the fuel is discharged. Under these a pressure greater than atmospheric pressure exists beneath the fire bed and in the said retort, and a certain amount of gas from the partially burned fuel is forced by the said pressure backward 5 through the fuel channel to the fuel hopper. This gas escaping from the hopper into the boiler room is known as hopper gas.

In the present invention, means are provided for preventing this gas from reaching 1 the hopper. This result is accomplished by providing a conduit connecting the fuel conduit with a part of the apparatus wherein the pressure is below that in said fuel conduit. By this means the hopper gas escapes from i the fuel conduit before reaching the hopper.

Other objects and features of the invention will be ap arent from the accompanying drawings and the following description and claims:

Figure 1 is a perspective view of a boiler supplied with fuel and air by means of a stoker and a forced draft fan and to which one form of the present invention has been applied. Figure 2 is a sectional view through a portion of the furnace of said boiler. Figure 3 is a fragmentary perspective View of a boiler to which another form of the invention has been applied. Figure 4 is a fragmentary perspective view of the front of a boiler to which another form of the invention has been applied.

In the drawings a boiler is supplied with fuel from a hopper 11 through a fuel conduit 12 by means of any suitable propulsion apparatus, such as a screw. The said screw may be driven by a motor 13 through suitable gears contained in a gear box 14. A motor 15 drives a blower or fan 16 which supplies air to the boiler through a conduit 17. The fuel conduit 12 discharges the fuel into a retort 18 above which the fuel is discharged into the fire bed 19. The air conduit 17 terminates in tuyeres 20, only one of which is herein shown but which are preferably positioned on either side of the retort 18 and from which air is discharged beneath the fire bed. Thus there atmospheric pressure beneath the fire bed which tends to force gases from the partially burned fuel backward through the fuel conduit 12 and out through the hopper 11.

In the form of the invention shown in Figure 1, a conduit 22, preferably of flexible construction, is connected to the fuel conduit 12 at a point approximately midway between the boiler and the hopper 11. The said conduit extends at its oppositeend through the front wall 23 of the boiler setting and thereby connects with the combustion space 21 above the fire bed. The pressure in said combustion space is normally at or about atmospheric pressure and, if the usual stack or other induced draft apparatus is used, the said pressure may be below atmospheric pressure. Since the pressure in the fuel conduit 12 is above atmospheric pressure, the gases returning therethrough are automatically drawn through the conduit 22 and are discharged into the said combustion space.

In the form of the invention shown in F igure 3, a conduit 122 is connected to the fuel conduit 12 and connects at its opposite end to the intake 123 of theblower 16. The presis a pressure greater than sure in this intake is always slightly below atmospheric pressure so that the gases are drawn from the conduit 12 in the same manner as in the form of the invention previous ly described.

In the form of the invention shown in Figure 4, the boiler front 223 is provided with a central fire door 224, having fastened thereto a pipe 225 having a downwardly-turned open end 226. The open end registers with the open end of an upwardly-extending pipe 227 carried by the fuel conduit 212. A small gap is permitted between the ends of the pipes 225 and 227. The hopper gas escapes through the pipes 225 and 227 to the coinbustion space of the boiler in the some manner as through conduit 22.

The form 'of the invention last described has two principal advantages,-first, the hopper gas conduit is movable with the fire door and is out of the way when the door is opened for inspection or cleaning of thefire, and, see- 0nd, a certain amount of air enters the hopper gas conduit through the gap between the ends-0f pipes 225 and 227. Under certain conditions obtained with the apparatus of Figure 1, the hopper gas entering the furnace through conduit 22 is so rich in combustible material and is heated to so high a tem- I perature near the furnace that combustion of the gases takes place in the conduit 22, The

conduit thereby becomes heated to an undesirable de ree of temperature. By the introduction of air into the conduit, the gases are diluted and cooled to such an extent that combustion thereof does not take place until they have entered the combustion space of the furnace. This result is accomplished without materially affecting the removal of the gas from the fuel conduit. I I

By means of the invention, the escape of hopper gas, into the boiler room is entirely eliminated. It isobvious that the invention may be applied to other forms of combustion apparatus than a boiler, It is equally applicable, for example, to hot air or hot'water furnaces or to Stoker-fired ovens for any industrial processes.

The invention claimed is: o

1. In combination with a furnace having a fire bed and a fire door communicating with the furnace space above said fire bed, a conduit through which fuel is mechanically supplied to said fire bed, means for supplyingair under pressure beneath said fire bed, a

conduit connecting 'said fuel conduit with said furnace space for removal of gases from said fuel conduit, said gas removal conduit including a portion carried by said fire door V and movable therewith, and a stationary portion carried by said fuel conduit, saidportions being in operative relation to each other when said door is closed, and being so s aced as to permit entrance of :air to the gases therein; 1 2. In combination with a furnace having a fire bed and a combustion space above said fire bed, a conduit through which fuel-is mechanically supplied to send fire bed, means for supplying air under pressure beneath said fire bed, and a conduit connecting said fuel conduit to said combustion space forwithdrawal of gases from said fuel conduit, said gas withdrawal conduit being arranged to permit entrance of airthereto to prevent undesired combustion therein.

In witness whereof, we have hereunto as fixed our signatures;

FRANK VERDRIE F. CLARK. 

